Hybrid drive vehicles utilize multiple sources of energy in order to improve fuel efficiency and economy while reducing vehicle emissions, and typically include a rechargeable energy storage device that is electrically connected to at least one of the multiple energy sources. The multiple energy sources often include an internal combustion engine and at least one motor/generator, and the rechargeable energy storage device is usually a battery or battery pack having a high energy density. Other hybrid drive vehicles may alternately employ a fuel cell or other power source in place of the internal combustion engine in order to further reduce vehicle emissions.
In a conventional or single power source vehicle, an alternator is typically used to convert mechanical energy from the fuel consumed in the internal combustion engine into electrical energy. The electrical energy is then used to continually recharge a single battery. During braking of such a conventional vehicle, the energy expended during braking is largely wasted. However, unlike such conventional vehicles, hybrid vehicles and certain other vehicles are able capture or harness a substantial amount of this otherwise wasted braking energy in a process commonly referred to as regenerative braking, thereby achieving a significant portion of their enhanced fuel economy.
During regenerative braking aboard a hybrid vehicle, an electric motor operates in reverse rotational direction to thereby slow the vehicle and, in the process, to generate useful electricity that can recharge the onboard energy storage device or battery. On certain production hybrid vehicles, the status of this regenerative braking process is communicated to the driver and passengers through various static or animated displays positioned on a center display, or through a power flow meter located on an instrument cluster. In either case, the driver benefits from the experience of “seeing” free energy being usefully recycled for other beneficial uses aboard the vehicle. However, typical vehicle display methods and devices are often not designed in such a way as to elicit a satisfying emotional response commensurate with the positive feelings drivers of hybrid vehicles often have in driving their fuel efficient vehicles, and may require averting attention from the road in order to fully appreciate the magnitude of energy transfer.